Method and apparatus for regulating rotary vibrators

ABSTRACT

A rotary vibrator for a vibrating feed system having a fixed mass and a partially free rotating mass on the shaft of the vibrator motor. Braking means being applied to the free rotating mass when the motor attains operating speed to displace the free mass about the shaft relative to the fixed mass in order to vary the thrust supplied by the vibrator to the system.

United States Patent 1191 Inventor: James Edward Brander, Cronulla,

- Australia Assignee: International Combustion Australia Limited, Australia Filed: Feb. 22, 1973 Appl. NO.I 334,568

Foreign Application Priority-Data Feb. 25, 1972 Australia 8086/72 U.S. c1....,..,.; 259/1 R; 74/87; 74/5735 References Cited UNITED STATES PATENTS Petrin 74/87 Brander Nov. 18, 1975 [5 METHOD AND APPARATUS FOR 3,061,079 10/1962 Morris 74/87 REGULATING ROTARY VIBRATORS 3,091,712 5/1963 Galbraith 3,505,885 4/1970 Waschulewski 74/61 OTHER PUBLICATIONS Machine Design, v61. 35, NO. 5, p. 127, 2/28/63.

Primary Examiner-Har'vey C. Hornsby Assistant Examiner-James A. Niegowski I Attorney, Agent, or FirmD. Paul Weaver [57] ABSTRACT A rotary vibrator for a vibrating feed system having a 1 fixed mass and a partially free rotating mass on the shaft of the vibrator motor. Braking means being applied to the free rotating mass when the motor attains operating speed to displace the free mass about the shaft relative to the fixed mass in order to vary the thrust supplied by the vibrator to the system. 1

8 Claims, 6 Drawing Figures US. Patent Nov. 18,1975 Sheet 1 of3 3,920,222

DIRECTION OF ROTATION FIG. 1

R (LARGE) DTRECTION OF ROTATION B FIG. 2

R (SMALL) U.S.- Patent Nov. 18, 1975 Sheet2of3 3,920,222

U.S-. Patent Nov. 18, 1975 Sheet 3 GT3 3,920,222

DIRECTION OF ROTATION FIG. 3

DIRECTION OF ROTATION A FIG. 4

METHOD AND APPARATUS FOR REGULATING ROTARY VIBRATORS BACKGROUND This invention relates to a method and apparatus for varying the thrust of rotary vibrators.

At the present time it is customary to use mechanical or electrical means for varying the'frequency and/r amplitude of vibrations in vibrator apparatus.

When mechanical means are used for varying frequency or amplitude, it has been common to use either a variable rate spring device which may include an air bag in conjunction with a vibrator such that the pressure in the air bag is adjustable to effect the change of spring rate, or some form of mechanical adjustment of a rotary vibrators position relative to the mass to be vibrated.

Low frequency long stroke vibrations have been used which utilize adjustable frequency A.C. drives, multispeed, and/or multi-winding AC. motors, or adjustable voltage D.C. drives or a further system which uses a combination of mechanical irnpedances and a remote control for changing the frequency and amplitude of the vibrator.

The aforementioned methods currently in use employ an electric motor with eccentric masses fixedly attached to the drive shaft of the motor. These methods suffer from various disadvantages which include high initial cost, and cost of maintenance due to brush wear, commutator problems and reduced motor bearing life.

In some cases the eccentric masses require to be positioned at various displacements around the shaft relative to each other in order to achieve changes in amplitude of the vibrator. These mass adjustments are tedious and time consuming as the vibrator needs to be stopped before the masses can be adjusted, particularly in circumstances which require rapid variations of frequency and/or amplitude of vibration.

SUMMARY OF THE INVENTION Themethod and apparatus of the present invention provides a means for independently or simultaneously varying the frequency and/or amplitude of a rotary vibrator.

In one general form the invention is a method of regulating the thrust of a rotary vibrator wherein there is at least one eccentric mass fixedly attached to the shaft of a vibrator motor and at least one further mass which is free to partially rotate about the shaft with respect to the fixed mass. If the partial rotation and the direction of rotation is arranged so that, in running up to normal operating speed of the motor, substantially maximum thrust is obtained, then the free mass will advance with respect to the fixed mass until a position of substantially minimum thrust upon the shaft is obtained.

Thereupon the method of the present invention employs a retarding force to the free mass, which may be achieved by any suitable means, such as electromagnetic braking in which a stationary magnet has poles ;which approach adjacent the revolving free mass or mechanical braking in which instance various arrange-.

ments of frictional drag may be used. Retardation of 2 Machines operating near or at resonance are well known in the art of materials handling using rotary vibrators. The effect achieved by this method occurs in machines in which the accelerations are due in part to spring-mass resonance but the effect is reversed with respect to another aspect of the present invention in that if the angle between the fixed mass and the free mass is such as to give minimum thrust while the motor is running up to normal operating speed, when such speed is obtained, the free mass will advance to give a position of maximum thrust.

reference may be made to the accompanying drawings,

in which:

FIG. 1 shows a fixed and a free mass of a rotary vibrator during run-up to operating speed;

FIG. 2 shows the relative positions of the two masses of FIG. 1 at operating speed and without the application of braking force to the free mass;

FIG. 3 shows a fixed and a free mass of a rotary vibrator which has opposite run-up and operating characteristics to that of FIG. 1;

FIG. 4 shows the relative positions of the two masses of FIG. 3 at operating speed and without any braking of the free mass;

FIG. 5 shows a side view of a rotary vibrator in accordance with the present invention coupled to a feeding pan via an intermediate spring system; and

FIG. 6 shows a plan view of the vibrator of FIG. 5.

DETAILED DESCRIPTION OF'THE DRAWINGS When a rotary vibrator motor with at least two ec centric masses on its shaft is used to drive a mass isolated through a spring system, and the weights differ in that one is rigidly fixed to the shaft of the vibrator motor and the other is free to partially rotate with respect to the fixed mass, an unusual phenomenon occurs.

If the partial rotation of the free mass and the direction of rotation is arranged so that in running up to the normal operating speed of the motor substantially maximum thrust is obtained as shown in FIG. 1, then the free mass 2 will, when normal speed is obtained, advance with respect to the fixed mass 1 until a position of minimum thrust is obtained (FIG. 2). It can be seen from FIG. 1 that the pin 3 located on mass 1 engages the mass 2 during the run-up of the motor which has axis of rotation 4.

In FIG. 1 the direction and magnitude of centrifugal force from the fixed mass 1 is shown by vector A and similarly by vector B for the free mass 2. It can be seen that the angle 6 between these two forces is small, therefore the resultant thrust which is the vector sum of these two forces is large.

Referring to FIG. 2 it is seen that the free mass 2 has advanced with respect to the fixed mass 1 and the resultant thrust R has decreased and by suitable choice of size of masses and the angle through which the free mass 2 may move the thrust can be reduced to as close to zero as desired. Then by applying a retarding force to the free mass, the angle between the fixed and free masses may be altered thus giving a variable thrust rotary vibrator motor. Means for retarding the free mass include but are not limited to electromagnetic braking in which a stationary magnet has poles which a roach close to the revolving free mass to provide eddy current braking; and mechanical braking in which case various arrangements of frictional drag are used.

Operation at or near resonance are well known in the art of materials handling using vibratory machines. The effect outlined above occurs in machines in which the accelerations are due in part to spring-mass resonance but the effect is reversed in a further embodiment of the invention in that if the angle between the fixed mass and the loose mass is such as to give minimum thrust while the motor is running up to normal operating speed then when normal operating speed is obtained, the free mass will advance to give a position of maximum thrust. Reference to FIG. 3 shows a fixed mass 5, a free mass 6, a stop 7 on the fixed mass 5 and a centre of rotation 8. The angle d) between the direction of centrifugal force vector A of the fixed mass 5 and the direction of centrifugal force vector B of the free mass 6 is large hence the resultant thrust R is small. Once normal operating speed is attained, the free mass advances as in FIG. 4 giving maximum thrust as the angle between vectors A and B is reduced. Braking or retardation applied to the free mass 6 permits in this case no retardation to give maximum thrust and maximum retardation to give minimum thrust.

If the mass on which the rotary vibrator motor is mounted is arranged to operate in either of the two modes outlined above, wherein the vibrator is either isolated from its surroundings by a spring system or operating close to resonance in all directions, the force required for retardation is substantial. However, as the two effects work in opposite directions, a balance can be obtained in which the mass moves in one direction isolated from its surroundings and in another direction moves in a spring-mass resonance system and consequently the retardation force to effect a change from one state to another becomes relatively small.

One form which the invention takes but which could be adapted by anyone well versed in the art is that shown in FIGS. 5 and 6.

A particular application of this invention will now be described in relation to a vibratory feeder as shown in FIGS. 5 and 6.

In the vibratory feeder depicted there is a rotary vibrator which includes a motor 9 with eccentric masses l0 and l 1 attached to the motor shaft 16, a feeder pan is isolated from the rotary vibrator by a spring system 14, the springs may be steel coil springs, leaf springs, elastomeric springs or other types used in the art or in particular the system as shown in our US. Ser. No. 308877 filed 22nd Nov. 1972. There are two pairs of masses l0 and 11, one pair at each end of the motor shaft, in this embodiment. One mass 11 of each pair is fixedly attached to the shaft 16 and the other mass 10 of each pair is free to rotate about the shaft. An electromagnet 12 is fixed relative to the motor casing and situated adjacent the periphery of each free mass 10. A counter mass 13 is provided on the vibrator, which permits adjustment of the relative accelerations in two directions, one direction being in line with the spring system 14 and the other direction being at right angles to the spring system.

Alteration of the disposition of the counterrnasses l3, and altering the relation between the operating speed of the motor and the natural frequency of the two mass (i.e. feeder pan and rotary vibrator) spring combination brings the accelerations in the two directions close to one another and the retardation force necessary to change from one state of thrust to another becomes relatively small. Indeed slight variation of motor voltage will also cause a greater change in the magnitude of acceleration in one direction than the other and this will also provide a large change in motor thrust for a small change in speed, as the relative angle between the weights will change.

What I claim is:

1. A rotary vibrator comprising a drive shaft, motor means for rotatably driving said shaft, a first and a second mass mounted at each end of said shaft, each said first mass being eccentrically mounted on said shaft for rotation therewith, each said second mass being eccentrically mounted adjacent respective first masses for angular motion relative to said first mass, intermediate spring means for coupling said vibrator to a mass to be vibrated, means for selectively changing the angular relationship between said first and said second masses during operation of said vibrator whereby the vibratory thrust imparted to the third said mass via said intermediate spring means may be controlled according to the users requirements, counterweight means on said vibrator for adjusting the relative accelerations of said vibrator in the direction of said intermediate spring means and perpendicular to said spring means whereby the force required to change the position of said second mass is minimal.

2. A rotary vibrator comprising a drive shaft, vibrator motor means for driving said shaft, a first eccentric mass mounted fixedly at each end of said shaft, a second eccentric mass mounted at each end of said shaft adjacent said fixed mass for angular relative movement with respect to said first mass, intermediate spring means connecting said vibrator to a mass to be vibrated, the maximum angular relationship between said first and second masses during operation being such that the frequency of the vibrations imparted by the vibrator is near to but below the resonance of said intermediate spring means; said vibrator further including means for controlling the angular relationship between said first and said second eccentric masses whereby the thrust imparted to the mass to be vibrated via said intermediate spring means may be adjusted, counterweight means for adjusting the relative acceleration of said'vibrator in the direction of the spring system and perpendicular to said spring system such that the variable force applied to change the position of said free mass is minimal.

3. A rotary vibrator as defined in claim 1, wherein the means to selectively change the angular relationship between the first and second masses comprises variable brake means mounted relative and adjacent to the periphery of said first and second masses.

4. A rotary vibrator as defined in claim 3, wherein said variable brake means comprises electromagnetic means for eddy current braking of said second mass.

5. A rotary vibrator as defined in claim 3, wherein said variable brake means comprises mechanical means for applying frictional drag to said second mass.

6. A rotary vibrator as defined in claim 2, wherein the means to selectively change the angular relationship between the first and second masses comprises variable brake .means mounted relative and adjacent to the periphery of said first and second masses.

7. A rotary vibrator as defined in claim 6, wherein said variable brake means comprises electromagnetic means for eddy current braking of said second mass.

8. A rotary vibrator as defined in claim 6, wherein said variable brake means comprises mechanical means for applying frictional drag to said second mass. 

1. A rotary vibrator comprising a drive shaft, motor means for rotatably driving said shaft, a first and a second mass mounted at each end of said shaft, each said first mass being eccentrically mounted on said shaft for rotation therewith, each said second mass being eccentrically mounted adjacent respective first masses for angular motion relative to said first mass, intermediate spring means for coupling said vibrator to a mass to be vibrated, means for selectively changing the angular relationship between said first and said second masses during operation of said vibrator whereby the vibratory thrust imparted to the third said mass via said intermediAte spring means may be controlled according to the user''s requirements, counterweight means on said vibrator for adjusting the relative accelerations of said vibrator in the direction of said intermediate spring means and perpendicular to said spring means whereby the force required to change the position of said second mass is minimal.
 2. A rotary vibrator comprising a drive shaft, vibrator motor means for driving said shaft, a first eccentric mass mounted fixedly at each end of said shaft, a second eccentric mass mounted at each end of said shaft adjacent said fixed mass for angular relative movement with respect to said first mass, intermediate spring means connecting said vibrator to a mass to be vibrated, the maximum angular relationship between said first and second masses during operation being such that the frequency of the vibrations imparted by the vibrator is near to but below the resonance of said intermediate spring means; said vibrator further including means for controlling the angular relationship between said first and said second eccentric masses whereby the thrust imparted to the mass to be vibrated via said intermediate spring means may be adjusted, counterweight means for adjusting the relative acceleration of said vibrator in the direction of the spring system and perpendicular to said spring system such that the variable force applied to change the position of said free mass is minimal.
 3. A rotary vibrator as defined in claim 1, wherein the means to selectively change the angular relationship between the first and second masses comprises variable brake means mounted relative and adjacent to the periphery of said first and second masses.
 4. A rotary vibrator as defined in claim 3, wherein said variable brake means comprises electromagnetic means for eddy current braking of said second mass.
 5. A rotary vibrator as defined in claim 3, wherein said variable brake means comprises mechanical means for applying frictional drag to said second mass.
 6. A rotary vibrator as defined in claim 2, wherein the means to selectively change the angular relationship between the first and second masses comprises variable brake means mounted relative and adjacent to the periphery of said first and second masses.
 7. A rotary vibrator as defined in claim 6, wherein said variable brake means comprises electromagnetic means for eddy current braking of said second mass.
 8. A rotary vibrator as defined in claim 6, wherein said variable brake means comprises mechanical means for applying frictional drag to said second mass. 